Over 40 million Americans suffer from hypertension. Timely diagnosis and control of high arterial blood pressure (AP) are crucial for preventing life-threatening complications and end-organ damage but have been hampered by the lack of nondisruptive monitors for 24-hour (including essential nighttime) AP tracking. Due to the epidemic proportions of AP abnormalities, an unobtrusive, cuff-free AP monitor will have a significant, lasting impact on the lives of millions of Americans, particularly those with cardiovascular risk factors and chronic cardiovascular diseases. Background: We have developed a technological platform for personalized, multiparametric monitoring of electrocardiogram, physical activity, symptoms and compliance with real-time, two-way, wireless transmission and pattern-recognition-based analysis on a smart phone and on an Internet server. Recently, to obtain pilot feasibility data for this project, we developed and tested: 1) a working prototype of a miniaturized, smart- phone-based system for noninvasive tracking of AP wave, and 2) a robust computational algorithm with personalized calibration for tracking the dynamics of systolic and diastolic pressure from characteristics of AP- wave velocity and energy. Pilot testing of this system in human subjects yielded promising results and reasonably accurate tracking of AP trends. We have also shown that peripheral vascular activity is the main confounder of the relationship between AP and AP wave in the peripheral vasculature. To obviate this confounding effect, we will examine feasibility of tracking AP waves in the central arteries using 3 types of sensor probes and identify optimal sensor type that provides stable AP-wave signal in the presence of the most common sources of motion artifacts and changes in body position. In Aim 2, the prototype system will be tested in healthy subjects with respect to the most common confounders, BMI and gender differences in torso/breast anatomy for a range of movements and changes in body position. The first application of the system is for nighttime AP tracking at home.